Equalized hydraulic brake



March 23, 1937.

5 Sheets-Sheet l Filed Jan.y 14, 19:52

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Uiu'ns)v STATES PA'rislSVrA OFFICE QUALIZED HYDRAULIC BRAKE- Herbert C; Bowen,A Detroit, Mich., ass-ignor to Hydraulic Brake Company, Detroit, Mich., a

corporation of Califorma I Application'January 14, 1932, Serial No. 586,474

2 12 Claims. (Cl. 60-54.5)

My invention pertains tof hydraulic brakes and tion for the purpose of more clearly illustrating 1s more particularly concerned with an equalized the piping arrangement;

- type of hydraulic brake system wherein separate Figure 3 is a vertical section of the compressor, conduits connect separate compression cylinders equalizer and reservoir unit taken'on the line 5 with separate braking elements. 3-3 of Figure 2; and I In the past it has been `proposedw'particularly Figure 4 is a diagrammatic View illustrating the in connection `with automotive vehicles, to use entire Systemhydraulic brake systems in which two separate Referring to the drawings, and more particuhydraulic brake layouts were operated from a l larly t0 Fig. 4 thereOf, I huVe illustrated my insingle pedal one layout applying the brakes to vention as applied to a hydraulic brake system 10 the front wheels of the vehicle and the other laywherein a manually operated pedal 5 is connected -out applying the brakes to the rear Wheels of the by suitable linkage to pistons 6 and 1 located revehicle. This arrangement hadthe disadvantage Spectvely in cylinders 8 and 9- The Cylinder 8 that the pressures in the two layouts were not isconnected to a discharge COnduit `lll leading always equal and that unequal braking connecto motor cyl ers II and I2 which for present l5 tion was obtained on the two sets of wheels. DurpSeS may De COnSidered aS heated at the .rear An object of my invention is to provide such a wheels of an automotive vehicle. The cylinder 9 system in which the pressures in the two layouts y is connected with a conduit 4I3 leading'to motorl will be maintained equal as long as both layouts cylinders I4 and I5 whichV may be considered as are in operating condition. y located at the'frontwheels of the vehicle. Each 20 Another object of my invention is to provide motor cylinder contains opposed pistons I (ik and .such a hydraulic brake system in which a failure .I'I which operate brake shoes I8 and I9 to move of one conduit system will not interfere with the them into engagement with brake drums ZIJ.Y The successful operation of the brakes applied by the brake shoes are provided with the usual retracvother conduit system. 1 tile springs 2l. f" 25, Another object is to provide an equalized hy- From' the foregoing it will bey apparent that draulic brake system which utilizes the pressure there is an operating layout consisting of piston existing in the l'owpressure conduit -to operate 6, cylinder 8, conduit I0 and motor cylinders I I means to .connect this low pressure conduit with and I2 4for operatingthe braking elements assothe high pressure conduit. ciated with the rear wheels of the vehicle; and a 30 'Anotherobject is to provide anequalized hyy separate layout consisting of the. piston l, comdraulic brake system in which the equalizing pression cylinder 9, conduit I3, and motor cylinmechanism will function throughout a prededers I4 and I5 for operating the braking elements termined range of pressure ratios between the associated with the front wheels o`i the vehicle. 'two conduits. Insofar as described the only connectionbetween 35 Another object is to provide'improved equalizthe two layouts is the mechanical connection ing means for .such a. system. whlchresults'from the fact that both layouts are Another object is to provide a new and im`- 'operated by the same pedal and this fact alone proved reservoir for reserve lluid. is not suflcient to maintain the proper operating 40 Another object is to provide an equalized hy-l relationship betWeen'ihe tWO .luYOlitS- I there? 40 draulic brake system which will be economical fore nd it desirable to connect the conduits I0 to manufacture and which will lbe sturdy and and '3 by my new and unproved, equallzels mdl' reliable in service. f cated generally by the reference character 22.

Other objects and 'advantages will appear as. In order ilo-provide a' system Whlcil is as com' f pact as possible Ihave shown the cylinders 8 .and 45 the description proceeds.

In the drawings, 9 as formed in a single casting. This casting has a rearward extension in which fis located the Flgllfre l 1S a' igmzonil Sectio? thrggl; the equalizer 22, and the yvertical Walls of the casting comp 6580.1" equa l er an/ reserfolr um o my extend upwardlyto provide a reservoirindicated I ew and .implfoved s ystem and 1s .taken on me generally by the reference numeral 23. As shown 50` Ime. |*'|0f' Flgure 3 U l most clearly in Figure 3, the reservoir 23 is divided Figure? 1.5 allelevalnon partly 1n SeetiOnOf the into sub-reservoirs 24 and 25 by a partition 26 COInDIeSSOr and equalizer unitlOf Figure 1'. thisA which, as illustrated, forms an integral part of usure 1s taken on the line 2-2 of Figure 3 except this same casting. v 'Ihis casting is further prothat one corner of the device is shown in elevavided with lugs2'l by means of which the casting 55 and mechanism supported thereby may be attached to the frame of the automotive vehicle.

The cylinder 8 is provided with a port 28 leading to the sub-reservoir 24 and the cylinder 9 is provided with a similar port 29 leading to the sub-reservoir 25. These ports 28 and 29 are so located that they are just in front of the rubber cups 3|! and 3l associated with the pistons 6 and 1 respectively' when the pistons and cups are in l their normal or fully retracted position, so that the cylinders 8 and 9 are normally in communication with their sub-reservoirs 24 'and 25 respectively. The upper ends of the sub-reservoirs .24 and 25 are almost closed by a horizontal 'plate l 32 secured to partition 26 by screws 33. The edges of the plate 32 however are just short of the walls of the reservoir so that fluid which is poured into the top of the reservoir can flow past the edges of the plate '32 and thence .into subreservoirs 24 and 25. The top of the reservoir is closed by a cover 34 secured'in place by bolts 35 and provided with a vent 36 which maintains the iluid in the reservoir under atmospheric pressure. This vent is preferably so located as to permit the entry of the minimum amount of dirt and moisture into the reservoir, and where it is,

desired or found necessary this vent may be supplanted by valve mechanism of the type disclosed in United States Patent No. 1,758,671l YA gasket 36 may be interposed between the cover 34 and top of the reservoir to provide a tight seal therebetween. 'I'he plate 32 serves as an anti- I splash means to prevent uid in one sub-reservoir from splashing over into the other sub-reservoir.

The pistons 6 and 1 are separably connected with and operated by the adjacent ends of piston rods 31 and 38. The other ends of the piston rods 31 and 38 are adjustably connected by screw threads or other suitable means with a cross member 39 40 connected to the operating pedal 5.

ySprings 40 and 4I are interposed between pistons 6 and 1` and valve mechanisms 42 and 43,

- the latter being shown as of the type disclosed in the` copending application of Erwin F. Loweke,

4,-, Serial No; 472,666, filed August 2, 1930, now

Patent No. 1,985,936. The springs 40 and 4I return the pistons 6 and 1 and their associated cups 30 and 3I to normal retracted position. The pistons 6 and 1 are of the type shown in Unitedl States Patent No. 1,764,179, and areprovided with iluid` sealing chambers 44 and 45 to prevent the entry` of air into the cylinders 8 and 9. The exposed ends of the pistons 6 and 1 are protected -against dirt and moisture by a-ilexible boot 46 ,-,5 of rubber or other suitable material.

The discharge end of thel cylinder 8 communicates\with a port 41 which leads to a threaded opening in which is located a suitable fitting 48 for connecting one end of the conduit III with the cylinder 8. The conduit I0, which is kin reality a conduit system connecting the compression cylinder 8 with the motor cylinders II and I2, includes anelbow portion 49 connecting fitting 48 with a T-tting 50. The T-fltting 50 and associated parts connect the conduit I0 with a plug 5I screwed into the casting containing the cylinders 8 and 9. The plug 5I has a central passageway 52 which divides to form passageways 53 and f 54 leading to a cylinder 55. The enlarged end 56 of a piston 51-'is located in the cylinder 55 and carries a flexible anfnular sealing member 58. The smaller end 59 of the piston 51 isl located in van intermediate cylinder 60 ofv smaller diameter than the .cylinder 55. This end 59 carries a flexible annular sealing member 6I which receives the thrust of a spring 62 which tends to maintain the piston v51 in the position shown with 'its projection 63 held in sealing engagement with a gasket 64 carried by the plug 5I. The piston 51 has a iluid passageway 65 which is reduced at one end as indicated at 66.

The discharge end of the cylinder 9 communicates with a port 61 which leads to a threaded opening in which is located a suitable fitting 68 for connecting one end of the conduit I3 with the cylinder 9. The conduit I3, or more properly, the 4conduit; system I3, includes an elbow vportion 69 connecting fitting 68 with T-fitting 10. The T-tting 10 and associated parts connect the conduit I3 with plug 1I screwed into the castingv containing the cylinders 8 and 9. The plug 1I has a central passageway 12 which divides to form' passageways 13 and 14 leading t0 a cylinder 15 which is of the same diameter as the cylinder 55 previously described. The enlarged end 16 of a piston 11 is located in the cylinder 15 and carries a exible annular sealing member 18. The smaller end 19 of the piston 11 is located in thefcylinder 60 and carries a flexible annular sealing member which receives the thrust of a spring 62 which tends to maintain the piston 11 in the position shown, with its projection 8l heldin sealing engagement withthe gasket 82 carried by the plug 1I. The piston 11 has a fluid passageway 83 which is reduced at one end as indicated at 84. The cylinder 60 is preferably provided with a bleeder screw 85 by means of which air may be bled from the equalizing mechanism.

My new and improved equalized hydraulic brake system is so designed that a break in either the conduit system I0 or the conduit system I3 will render theequalizing mechanism inoperative and will permit the other conduit system and the compressor mechanism and motor cylinders connected therewith to function normally. To this end I have so' designed my equalizer mechanism that in order for this equalizer mechanism to function to equalize the pressures in the two conduit systems the pressure in the low pressure conduit system must be suiciently great to bear a predetermined relationship `to the pressure in the high pressure conduit system. This relationy ship is determined when the system is designed and is dependent upon the ratio between the area of the cylinder 60 and the area of the cylinder 55. As previously explained, the cylinder 15 is given'the same area as the cylinder 55. These areas are selected tof give the desired ratio and in so selecting these vareas the force exerted by the spring 62 is taken into account.

In one embodiment of my invention I have found it desirable to construct the apparatus so that the-pressure in the low pressure conduit must be at least half as great as the pressure in the high pressure conduit in order for the equalizer mechanism to operate. In this embodiment the area of the cylinder 60 is made slightly less than half the area of the cylinder 55, the reason for making the area of the cylinder 60 less than halfthe area of the cylinder 55 being to compen- `sate for the force exerted by the spring 62 in this particular embodiment, the pressure in the, conduit system II) rises'immediately to 60 lbs. per square inch upon actuation of the pedal,

whereas the pressure in the conduit system I3 rises only to 40 lbs. per square inch, the equalizer mechanism will function to permit the flow of iluid from the conduit system I0 into the conduit system I3 and thereby equalize the pressures in the two conduit systems. In this operation of the equalizer mechanism the enlarged end 56 of the pistonv51 is subjected to the pressure of 60 lbs. per square inch existing in the conduit 5 system I0 whereupon the piston 51 is moved downwardly as viewed'in Fig. L'th'ereby moving the extension (i3-.away from the sealing washer 54 and permitting uid to ilow, from cylinder 554 through passageways 65 and 66 into, cylinder 60.

l The piston 51 continu s to move downwardly until the lower end of tl'enlarged part 56 abuts the shoulder formed at cylinders 55 andfrll whereupon the piston 51 comes to rest.

l5 The pressure in the cylinder 60 vis-now 60 lbs.

per square inch, that is, the same pressure as y `'exists in the conduit system I0. The small end of pistonf11 is thus subjected to this 60 lbs. pr'esvsure and also the light pressure of the spring 62, 2O whereas the large `end of this piston is subjected to the 40 lbs. pressure existing in the conduit system I3. As previously explained,`the.for ce exerted bythe spring 62 may be disregarded. The effective pressure acting on the small end of the piston 11 to-hold it in the position shown would be sixty times one-half or lbs. if we cong Fig. 1. This force moves the' piston upwardly "d until the shoulder Aformed by the upper end of the large portion ofthe pistonseats against the shoulder formed vat the juncture between cylinders 60.and 15 whereupon thepiston comes toi As soon as the extension 8l moves away y rest. 40 from the gasket 82 fluid canow fromicylinder through passageways 84 and 8?4 int'o cylinder. 15 and from there to conduit system I3, and since cylinder .60 is already in communication with conduit system l0 a direct connectionis established between' conduit system lll and conduit system I 3 so that iluidv can flow from co'nduit system INinto conduit system .I3 and equalize the pressures in the two systems,

If vthe pressure in conduit system I3 had been 50 only 20 lbs. per square inch instead of 40 lbs. per square inch, piston 11 would have remained in the position shown in Fig. `1 of the drawingsv since -the force acting on its large end would have been 20 times. one or 20 lbs. whereas the 5 force acting 'on "its small end wouldvhave been .30 lbs. and the piston would not have moved away from the washer 82 but would have been urged thereagainst by a force of 10 lbs. actingdownwardly 4on the piston.A

G0 In the normal operation of the brake system where the pressures developed in' the conduit systems I0 and I3by their respective pistons 6` and 1 are substantially equal, the pistons 51 and 11-'are moved away from their respective gaskets` 64 and 82 as soon as pressure is applied to the brake system and said pistons remain separated from said gaskets until pressure on the system is relieved. It is possible that a rela# tively large leak might occur in one of the' con-v duit systems while the pistons 51 and 11 are awayfrom their respective gaskets', that is, while there is an 'open connection through the equalizer mechanism through which fluid can flow from one conduit-system to the other. I accordingly make the passageways .66 and 84 relatively small so he junction betweenr is insufficient to maintain pressure in a conduit system which has a fast `leak and therefore the pressure in the conduit system with the-large leak will drop and the piston 51 or 11 which is held open by the pressure in such leaking conduit-system will return to the positionA shown in ,Fig. 1 and cut oi communication between the two conduit systems. The pressure in the good conduit system is thus preserved and the brakes -connected therewith will function perfectly inspit'e of the leak in` the other conduit system, and

the resultant failure`or ineffective operation of the brakes connected -to the leaking conduit system. i

When it is desired to bleed the cylinders and conduit systems of anyair which may have worked its way thereinto the bleeder screw is unscrewed one or two turns'and the pedal actuated to cause the pistons 6 and 1 to discharge uid into the conduit systems.7 The air in thelequalizer mechanism will thereupon be discharged ythrough the bleeder screw 85 and as soon as fluid free from air comes outof the bleeder screw 85 this Ascrew may be returned-to normal sealed position.

In accordance with the usual practice the motor cylinders are provided with similar bleed Screws whereby any air existing in the conduit systems or motor cylinders may bleed therethrough.

While-I have illustrated a single embodiment of 'my invention it is to be understood that my invention is not limited to the details of the disclosure herein but may be incorporated in numerous modifications thereof and that thescope of my invention is limited solely by the following claims.

I claim: f I' l 1. In a hydraulic brake system of the class described,.'the vcombination of a compression cyl.-

inder,a motor cylinder, a conduit connecting said cylinders, -a second compression cylinder, asecqnd motor cylinder,.a second'conduit connecting said second cylinders, s aid compression cylinders being operable to createfluid pressure in vsaid conduits and motorv cylinders, an equalizng mechanism connecting said conduits for uid communication J therebetween, said mechanism including a pair of valves controlling communication between said conduits, each valvehaving opposing surfaces of diierent area adapted for exposure to uid pressure, and uid. supply means for said compression cylinders. l A

2. In mechanismI of 'the l.class described, the combination of compressing means, motormeans,

- a conduit connecting said means, a second compressing means, a ,second motor means, a second conduit connecting said second means, said com- Y for exposure to fluid pressure, seats for said valves,

and means normally holding said valves against said seats. I

3. In a hydraulic brake system of the class described, the combination of a casting providing two cylinders and a reservoir, there being a port connecting each cylinder with said reservoir, a

partition in said reservoir, said partition being located between said ports, a cover for-said reservoir spaced above lthe top of said partition,

land antisplash means mounted on said partition A smaller cylinder interposed therebetween, a differential piston having one end in one of said large cylnders and another end in said'smaller cylinder, a second piston having one end in the other large cylinder and a second end in said smaller cylinder, there being conduit means for establishing communication between said cylinders, and valve means controlled by said pistons. 5. In mechanism of the class described, the

combination of a first compressing means, a first,

motor means, aA conduit connecting said means, a second compressing means, a second motor means, a second conduit connecting said second means, an equalizer mechanism connecting said conduits, and ow restricting means in said equalizer mechanism.

6. In.' mechanism of the class described, the combination of a first compressing means, a iirst motor means, a conduit connecting said means, a second compressing means, a second motor means, a conduit connecting said second means, an equalizer mechanism for establishing iiuid communication between said conduits, means actuated bythe difference in pressure in said conduits for rendering said equalizer mechanism inoperative when the pressure difference between said conduits exceeds a predetermined amount, means for operating said compressing means, and elements operated by said motor means.

7. In a hydraulic brake system of the class described, the combination of` a rst compressing means, a second compressing means, a iiuid reservoir, there being a port connecting each compressing means with said reservoir, apartition in said reservoir, said partition being located between said ports, and an antisplash plate carried by said partition and extending almost to the walls of said reservoir.

8. In mechanism of the class described, an equalizer comprising two large and one small cylinder, a piston in each of said large cylinders,

-each piston having a part extending'into said 4small cylinder, said pistons providing passageways therethrough, 'means for closing said passageways, and bleeding means associated with one of said cylinders. y

9. In a system of the class described, an equalizer mechanism including two large cylinders., a small lcylinder connecting said large cylinders, a piston in each of said large cylinders, said pistons having restricted passageways therethrough, closure means for said passageways, said pistons being reciprocable, and means biasing said pistons towards said closure means.

10. In mechanism of the class described, the

combination of a rst compressing means, a first motor means, a conduit connecting said means,

\a second compressing means, a second motor means, a second conduit connecting said means,

, an equalizermechanism connecting said conduits,

flow restricting means in said equalizer mechanism, and iiuid pressure valve means controlling said last-named means.

11. In a fluid pressure system of the class described, the combination of a pair of compression cylinders, a pair of motor cylinders, a conduit connecting each compression cylinder with one motor cylinder, a pressure diierence control means connecting said conduits and providing for limited ow therebetween upon the creation of certain predetermined conditions, said lastnamed means including a differential valve having opposed surfaces of different, areas, one, surface being exposed to the pressure created in one of said conduits and the other surface being exposed to the pressure created in the other of said conduits.

12. In a hydraulic brake system of the class described, the combination of a first compressing means, a second compressing means, a uid reservoir having a bottom and side walls, there being a port connecting each compressing means with said reservoir, a partition Ain said reservoir, said partition being located between said ports, projections on said side walls, and antisplash means for said reservoir, said antisplash means compising a plate of slightly less area than the interior of said reservoir and resting on said par- 

